1. Field of the Invention
The present invention relates to a V-belt type continuously variable transmission, a saddle-ride type vehicle provided with the V-belt type continuously variable transmission, and a method of manufacturing the V-belt type continuously variable transmission.
2. Description of Related Art
A motorcycle with a V-belt type continuously variable transmission is known (see, for example, JP-A-2003-301903, JP-A-2002-106658 and JP-A-09-026006). As described below, there is a problem associated with the process of assembling such conventional V-belt type continuously variable transmissions.
FIGS. 13-17 illustrate an assembly process of a conventional V-belt type continuously variable transmission in a motorcycle. FIG. 13 shows a state, in which assembly of the V-belt type continuously variable transmission is finished. A V-belt type continuously variable transmission (referred below to as CVT) 530 comprises a primary sheave 571, a secondary sheave 572, and a V-belt 573 wound around the primary sheave 571 and the secondary sheave 572.
The primary sheave 571 comprises a stationary sheave half 571a positioned outward in a vehicle width direction (a left and right direction in the figure) and a movable sheave half 571b positioned inward in the vehicle width direction and opposed to the stationary sheave half 571a. The stationary sheave half 571a is clamped and fixed to a right end of a primary sheave shaft 546c by a lock nut 615 to rotate with the primary sheave shaft 546c. The movable sheave half 571b rotates with the primary sheave shaft 546c and is slidable axially of the primary sheave shaft 546c. Also, a cam surface 611 is formed on a left portion of the movable sheave half 571b and a cam plate 612 is arranged on the left of the cam surface 611. A roller weight 613 is arranged between the cam surface 611 and the cam plate 612.
The secondary sheave 572 comprises a stationary sheave half 572a positioned inward in the vehicle width direction and a movable sheave half 572b positioned outward in the vehicle width direction and opposed to the stationary sheave half 572a. The movable sheave half 572b is mounted to the right end of a secondary sheave shaft 562. The movable sheave half 572b rotates with the secondary sheave shaft 562 and is slidable axially of the secondary sheave shaft 562. The stationary sheave half 572a comprises a sheave body 572c, which is substantially in the form of a doughnut plate and around which a V-belt 573 is wound, and a substantially cylindrical-shaped boss portion 572d extending rightward from a right side of the sheave body 572c. The sheave body 572c and the boss portion 572d are welded to each other to be formed as an integral body. Also, the boss portion 572d is spline-fitted onto the secondary sheave shaft 562.
A cylindrical-shaped boss 617 fixed to a shaft core of the movable sheave half 572b is provided on the boss portion 572d to be slidable axially of the boss portion 572d. A slide groove 617a is formed on the boss 617 to be slit. A guide pin 618 is implanted in the boss portion 572d and engages slidably with the slide groove 117a so as to rotate with the boss 617.
A spring bearing member 619 comprising an annular plate is mounted on a tip end of the boss portion 572d of the stationary sheave half 572a by a circlip 619a. A coil spring 620 in a compressed state is interposed between the spring bearing member 619 and the movable sheave half 572b. The secondary sheave shaft 562 and the stationary sheave half 572a are fixed to each other by a lock nut 616 provided on the secondary sheave shaft 562.
In an assembling process of the CVT 530, the secondary sheave 572 is assembled separately and mounted to the secondary sheave shaft 562, and then the movable sheave half 571b and the stationary sheave half 571a of the primary sheave 571 are sequentially mounted to the primary sheave shaft 546c. 
That is, as shown in FIG. 14, for the primary sheave 571, the cam plate 612 and the movable sheave half 571b are inserted through the primary sheave shaft 546c. Subsequently, the V-belt 573 is wound around the primary sheave 571 and the secondary sheave 572 in a state in which the stationary sheave half 571a is not mounted to the primary sheave shaft 546c. 
When the CVT 530 is used, the boss 617 of the movable sheave half 572b and the stationary sheave half 572a on the secondary sheave 572 do not abut against each other. In the state described above, however, the movable sheave half 572b is exerted by only the bias of the coil spring 620, so that it is put in a state of abutting against the stationary sheave half 572a. Therefore, a clearance between the movable sheave half 572b and the stationary sheave half 572a, that is, a belt groove, becomes narrow and a part of the V-belt 573 protrudes from the secondary sheave 572. In order to move the V-belt 573 toward a center of the secondary sheave 572, it is necessary to separate the stationary sheave half 572a and the movable sheave half 572b from each other against the bias of the coil spring 620.
When attempting to mount the stationary sheave half 571a (indicated by two-dot chain line in the figure) of the primary sheave 571 to the primary sheave shaft 546c as shown in FIG. 15, in a state in which the V-belt 573 shown in FIG. 14 protrudes, the stationary sheave half 571a cannot be arranged in an appropriate position since the V-belt 573 approaches excessively toward a center. Attempting to forcibly clamp the lock nut 615 (see FIG. 13) in such state creates a risk of breaking stationary sheave half 571a or the V-belt 573.
Therefore, in a conventional assembling process, a jig (not shown) or the like is used as shown in FIG. 16 to enlarge an interval between the stationary sheave half 572a and the movable sheave half 572b on the secondary sheave 572 to move the V-belt 573 toward a center of the secondary sheave 572. At this time, the V-belt 573 is arranged outward relative to a position, shown in FIG. 15, on the primary sheave 571. While this state is maintained, the stationary sheave half 571a of the primary sheave 571 is mounted to the primary sheave shaft 546c to clamp the lock nut 615 as shown in FIG. 17. In the state shown in FIG. 17, the stationary sheave half 571a of the primary sheave 571 is clamped and fixed by the lock nut 615 in an appropriate position. When the jig is removed after the stationary sheave half 571a is mounted in this position, the V-belt 573 is also arranged in an appropriate position.
As described above, in a conventional assembling process of the CVT, the interval between the stationary sheave half 572a and the movable sheave half 572b on the secondary sheave 572 must be forcibly enlarged against the bias of the coil spring 620. In addition, while the interval is enlarged, it is necessary to move the V-belt 573 outwardly of the primary sheave 571 (see FIG. 16) and to mount the stationary sheave half 571a of the primary sheave 571 while maintaining such state (see FIG. 17). Accordingly, with the conventional process, an exclusive jig is needed, a large force is necessary, and the process is complicated. Therefore, the manufacture of the CVT is not satisfactory in yield.
Also, the boss portion 572d, which constitutes the stationary sheave half 572a of the secondary sheave 572, is usually subjected to surface treatment as by plating processing in order to prevent abrasion. Since the stationary sheave half 572a is formed integrally by fixing the sheave body 572c and the boss portion 572d together, however, it is necessary to apply masking for surface treatment only on the boss portion 572d, so that work becomes complicated.
Further, since the sheave body 572c and the boss portion 572d are fixed together by means of welding processing, increased manufacturing costs and deterioration in processing accuracy are liable to occur. On the other hand, it is possible to fix the sheave body 572c and the boss portion 572d together by means of rivets. In case of fixation with rivets, however, the secondary sheave 572 is increased in size (in particular, increased in diameter), which is disadvantageous in terms of arrangement space.